Railroad hopper cars have been used for years to transport particulate and granular material such as grain and the like. Covered railroad hopper cars have been constructed and arranged with a roof for protecting the railcar contents from contaminants and weather related elements. Access to an interior of the railcar from above is through a hatch opening in the roof of the railcar. One type of railcar in wide spread use presents a hatch opening typically extending the length of the railcar. In some railcar designs, the hatch opening can be configured with arcuate end portions. Cowled coaming, upstanding from the roof, typically extends circumferentially or peripherally about the hatch opening.
The hatch opening in the roof of the railcar is closed during transport by a series of individual hatch covers typically arranged in end-to-end relationship relative to each other. The hatch covers are usually pivotally connected to the roof along one side thereof and can be swung to an open position. In one form, each hatch cover can measure in length from eight to thirteen feet and weigh approximately 100 pounds. Suffice it to say, the hatch covers are sized to extend across and over a top rim of the coaming to cover the hatch opening. Typically, the hatch covers are secured in a closed position during transport by a series of batten bars and hold downs.
Known hatch covers used to close hatch openings in covered hopper cars suffer from numerous problems. One form of known hatch cover is formed of fiberglass or other suitable moldable material. Fiberglass hatch covers, however, are susceptible to deteriorating ultraviolet rays as well as weather related deterioration factors. Fiberglass hatch covers must be designed and manufactured with reinforced profiles for accommodating mounting of several hinge structures along the length thereof to allow pivotal movement of the hatch cover between open and closed positions. As will be appreciated, the need for reinforced profiles adds to the complexity of the hatch cover design. Moreover, the need for high temperatures and pressures in the hatch cover molding process leads to relatively high cost and other obvious problems. Additionally, the molding compound does not readily flow into deep ribs, bosses and related reinforcement areas of the hatch cover. Accordingly, reduced reinforcement and a decreased stiffening effect often results from imperfect formation of the hatch cover.
Although specifically directed not to walk across or stand on such railcar hatch covers, it is inevitable workers tend to stand or walk across the closed hatch covers as commodity is added or loaded into the railcar. Accordingly, hatch covers have typically been structurally designed with a “hat” section profile as an attempt to add strength and stiffness to the hatch cover. As will be appreciated, requiring such a profile adds to the complexity of the hatch cover design along with manufacturing process and, again, adds to the overall cost of the hatch cover. Moreover, the need for such a profile to accomplish rigidity and stiffness increases the weight of the hatch cover whereby detracting from the overall carrying capacity of the railcar.
Additionally, known railcar hatch covers typically include generally vertical sidewall structure arranged on opposite lateral sides of the longitudinal centerline of the hatch cover and which depend from a center section of the hatch cover. Each depending sidewall is joined to the center section of the hatch cover. Since each depending sidewall terminates below the top rim of the coaming, the sidewalls of the hatch cover advantageously inhibit dirt and related debris from passing between the hatch cover and the top rim of the coaming.
A problem has developed in known hatch cover designs. Cracks have been known to form in the material used to form the hatch cover. In some designs, such cracks have occurred and radiated in a corner region where the generally vertical depending sides of the hatch cover are joined to the center section of the hatch cover. It appears the cracks may be formed by the concentration of stress at the corner regions of the hatch cover. Such cracks allow water, and related contaminants to leak through the hatch cover thereby damaging the contents of the railroad hopper car. This is simply unacceptable.
Moreover, the Association of American Railroads (“AAR”) has developed and established standards which set forth specific and requirements for the design and development for railcar hatch covers. One such standard established by the AAR defines specific criteria for maintaining the hatch cover in a predetermined sealing relationship with the top rim of the coaming when the hatch cover closed. Hatch covers must be sufficiently rigid to qualify under this and related AAR standards. In those hatch cover designs wherein the length of the hatch cover can measure up to thirteen feet between opposite ends thereof, this standard presents difficult design challenges.
Thus, there is a continuing need and a desire for a railcar hatch cover which has a simplistic lightweight design, and offers enhanced strength and stiffness over comparable known railcar hatch covers.